Crustal Velocity Structure of the Deep Continental Subduction Zone — A Wide Angle Reflection/Refraction Seismic Study on the Eastern Dabie Orogen

Abstract

AbstractSix two‐dimensional crustal structure profiles in the eastern Dabie, Anhui Province, have been obtained by wide‐angle seismic reflection/refraction exploration. The results reveal that the crust of the eastern Dabie orogen presents a high‐velocity dome, the middle‐ and lower‐crust's metamorphic rocks exposed on the surface in the core of the dome, where the velocity approaches to 5.0 km/s. A low velocity layer (body) about 6.1 km/s has developed in the upper‐middle crust on it's both side wings. The depth of the Moho discontinuity varies greatly from about 41km in the core to 32–34km in the surrounding area, and a 4km Moho‐offset is observed beneath the Xiaotian–Mozitan Fault. We recognize that the eastern Dabie orogen shows a typical velocity‐pattern of continent‐continent deep subduction/ collision. The Moho offset should be related with the deep subduction of the Yangtze block and represents the suture zone between the Yangtze/North China Blocks. Therefore, the high‐velocity dome may be a result of collision/extrusion between the two continental blocks and the low‐velocity layers (bodies) mentioned above may play an important role in the post‐collisional crust extension and exhumation of the ultra‐high pressure metamorphic rocks.